Maintaining the structural integrity of certain components and structures is very important in many areas of industry, for example, the aviation and automotive industries, due to safety concerns and the like. Loss of structural integrity can be caused by material defects, such as disbonds, delaminations, cracks, corrosion, inclusions, and/or voids that may exist in the structure or component. For example, it is important in the aviation industry that non-invasive, reliable inspection techniques exist to examine the structural integrity of the aircraft skin, fuselage and structural components of the aircraft to prevent the likelihood that the aircraft does not suffer from structural failure during operation. Therefore a point by point inspection of airplanes is sometimes required. Similarly, by way of example, non-invasive inspection and analysis of the automobile frame components and engine components is also often important. Therefore, non-invasive and non-destructive inspection techniques and methods have been developed and are currently utilized in various industries to analyze and inspect the structural integrity of various materials and components.
One current method for non-invasive analysis of materials and/or components for defects includes treating the material or component with a dye penetrant such that the dye enters any crack or defect that may exist. The component is then cleaned and then treated with a powder that causes the dye remaining in the defects to wick into powder. Next, ultraviolet light is applied to the material or component causing the residual dye remaining in any cracks or defects to fluoresce. This technique has drawbacks however. The dye sometimes is not suitable to identify cracks that located in areas other than the surface of the component. In addition, this technique is can be operator dependent in that the person performing this technique should be adequately trained and skilled.
Other methods currently utilized for the non-invasive analysis and inspection of materials and components include use of an electromagnetic current and use of thermal imaging including ultrasonic excitation or ultrasonic thermography.
The non-invasive analysis method of using an electromagnetic current is carried out by employing an electromagnetic coil to induce eddy currents in the test material or component. The current pattern changes at the location of a defect or crack. This technique requires point by point inspection, which can be labor intensive and is to some extent limited to only specific types of defects. In addition, the evaluator must be properly trained and skilled.
Ultrasonic thermography is a non-invasive analysis method by which a part or portion of a component, material and or structure is “excited” with a high power ultrasonic pulse using an ultrasonic transducer. The resulting vibration of the part under test causes, for example, differential motion across a crack face, producing friction and causing the crack to “heat-up” while the undamaged part of the component is only minimally heated by the ultrasonic waves. The increased heat that diffuses to the surface from the crack causes a local temperature increase that can be detected with an infrared camera. Similarly, the ultrasonic thermography technique can be utilized to identify disbonds and delaminations where the surface temperature above such defects increases due to acoustic damping and again, these areas are located by using an infrared camera.
The ultrasonic thermography technique has been successful for detecting defects in materials and/or components, however current analysis systems employing ultrasonic thermography technique have drawbacks. Some current ultrasonic thermography systems are designed for laboratory use where only small specimens can be analyzed. Therefore those systems are not always well suited for field inspection of materials or components or for inspection of materials that are large in size, for example, fuselages and flight control structures of in-service airplanes. In addition, many of the current ultrasonic thermography systems require manual alignment and placement of the ultrasonic transducer and may not provide a consistent pressure between the traducer and the test surface or part, which can negatively affect the repeatability and accuracy of the technique. Too much or too little pressure may inhibit repeatable detection. In addition, misalignment of the transducer can cause the part or surface being inspected to be cut or burned.
Accordingly, it is desirable to provide a method and apparatus for detecting multiple defect types in both metal and composite structures. It is also desirable to provide an apparatus and method for effectuating the quick and efficient inspection and analysis of large components and/or materials, such as airplane fuselages and structures, in real-time. It is further desirable to provide a repeatable analysis method and apparatus utilizing ultrasonic thermography for effectuating inspection of large components or areas to detect cracks, disbonds, and/or corrosion.